Flexible display

ABSTRACT

A flexible display includes a plurality of pixel chips, chixels, provided on a flexible substrate. The chixels and the light emitters thereon may be shaped, sized and arranged to minimize chixel, pixel, and subpixel gaps and to provide a desired bend radius of the display. The flexible substrate may include light manipulators, such as filters, light convertors and the like to manipulate the light emitted from light emitters of the chixels. The light manipulators may be arranged to minimize chixel gaps between adjacent chixels.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/019,144 filed on Jan. 4, 2008.

FIELD OF INVENTION

The present invention relates to display devices. More particularly, thepresent invention comprises a flexible display.

BACKGROUND

There has been increased interest in the development of flexibledisplays. It has proven difficult, however, to produce a large flexibledisplay, as manufacturing techniques used to produce small-scaledisplays have not proven readily scalable. Presently, large scaledisplays tend to be heavy, expensive, non-flexible, unreliable and powerhungry.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a flexible display includes a plurality ofself-contained pixel-containing chips, called chixels, that are arrangedon a flexible substrate in a manner that provides sufficient bend radiusto the substrate to allow flexing of the display. The chixels mayinclude a sub-array of pixels provided on a rigid substrate that may besealed to form a modular unit. A chixel can be combined with otherchixels on a flexible substrate so that multiple pixel sub-arrayscombine to form a large pixel array for a display. The chixels may berigid units of a predetermined size and shape and arranged on thedisplay substrate in a manner to provide a desired bend radius to thesubstrate and produce a display having a desired degree of flexibility.

The flexibility of the chixel display is a function of the bend gapsbetween the chixels. As used herein the term “bend gap” refers to thespace between adjacent chixels. Generally, the smaller the chixels, thegreater number of bend gaps and the more flexible the display. A chixelmay be formed in a particular shape and arranged on a flexible substratein such a way as to provide a chixel-based display of a desiredflexibility. For example, a chixel may be square-shaped and have an n×npixel arrangement, such as a 4×4 arrangement, to allow similarflexibility in both the horizontal and vertical planes. To increaseflexibility in one particular plane more than another, the size of thechixel in that particular plane may be decreased to provide more bendingpoints. For example, a pixel arrangement including elongatedrectangular-shaped chixels having a 4-row×8-column pixel arrangementthereon may provide twice as many vertical gaps as horizontal gaps andthereby provide greater lateral flexibility. Furthermore, chixels ofdifferent sizes or shapes may be incorporated into a display tocustomize the flexibility of different portions of the display.

In an exemplary embodiment of a chixel, a plurality of light emitters isprovided on a rigid substrate and serves as subpixels of a display. Thesubpixels may be divided into groupings, such as groupings of threesubpixels, to form pixels. For example, subpixels that emit red, greenand blue light may be grouped together to form an RGB pixel. Otherarrangements, such as by way of example and not limitation, include amonocolor display in which all subpixels or pixels emit the same colorlight. Additionally, the light emitted by the pixels or subpixels may beconverted or filtered to provide the desired light output; for example,the pixels could be formed of blue LEDs that are filtered or are colorconverted and filtered.

The subpixels may be of rectangular shape so that when combined withother subpixels they form a square pixel. For example, each subpixel maybe of a size ⅓x×x, so that three subpixels placed side-by-side form asquare pixel of size x×x. The pixels may be arranged on the substratesuch that the space between adjacent pixels, referred to herein as a“pixel gap,” is of a desired distance d1. Because there are no pixels toproduce light at the pixel gap, the gap may appear as a darkened area ofa display, referred to as a “pixel gap line.” Similarly, the subpixelsmay be uniformly spaced so that space between subpixels, the “subpixelgap”, is of a desired size.

In one aspect of the invention, the pixels are of a size relative to thepixel gap to make the pixel gap line less noticeable to a viewer. Forexample, the pixels may be of a size relative to the size of the pixelgap so as to provide a display of a desired resolution in which thepixel gap is not as pronounced or distracting to the viewer. Thisrelationship and sizing may depend on a number of factors, including,but not limited to, viewing distance, contrast ratio, brightness, andviewing environment.

As mentioned above, the chixels are provided on the flexible displaysubstrate adjacent other chixels. The distance between the chixels isreferred to herein as a “chixel gap.” In an exemplary embodiment thechixels are arranged so that the chixel gap in minimized and the “pixelgap” between adjacent pixels is uniform throughout the display, evenacross adjacent chixels. In another exemplary embodiment the subpixelgaps are uniform within a chixel as well as between adjacent chixels.

The subpixels and pixels of the chixels may comprise various lightemitters. In one exemplary embodiment, a chixel comprises subpixels andpixels formed of light emitted diodes (LEDs). In an exemplary method ofmaking an LED-based chixel, a plurality of LEDs is prepared on a rigidsubstrate. For example, an n-doped layer and a p-doped layer areprovided on a rigid substrate, such as glass or sapphire wafer to formLED layers. Various layers may be used in the LED manufacturing processto produce LEDs which emit light with desired properties. For example,various phosphor layers may be used to produce light of desiredwavelengths and color. These layers may be provided to the bottom of thesubstrate. For example, a photoconversion layer may be provided on thebottom of the rigid substrate to convert blue emitted light into whitelight which is more efficiently filtered to different colors. In oneexemplary embodiment of the invention, a light manipulator may be added.For example, filters made of coextruded polycarbonate plastics, surfacecoated plastics, or deep dyed polyesters may be provided to convert thelight emitted from the LEDs to a light with desired characteristics. Forexample, most filters are subtractive, allowing only a portion of theemitted light to pass through the filter. For example, filters and colorconversion techniques may be used to provide light of desiredproperties. For example, filters may be used to produce red and greenlight from emitted blue light. The dyes for the filters may be optimizedto produce the desired wavelength of light output from the light emittedfrom the LED. A color conversion phosphor may be deposited over the blueLEDs to produce a white light emission that may then be filtered intodesired colors, such as red, blue, and green. The filter film could beprovided to the chixel or to the flexible substrate to which the chixelsare attached.

Portions of the LED layers may then be removed by etching or other knowntechniques to form a plurality of spaced-apart LED stacks that share thesame substrate. For example, portions of the LED layers could be removeddown to the rigid substrate so as to provide LED stacks that share thesame substrate. The particular size of the LED stacks can vary accordingto the use to the use of the display. For example, for displays meantfor close viewing the LEDs can be etched into smaller stacks thandisplays meant for viewing at greater distances.

Contacts may then be provided to the LED stacks to form a plurality ofspaced apart LEDs on a rigid substrate that together form an LED wafer.The LEDs may be provided with rear contacts so that rear display driversmay be used to drive the display in which the chixels are incorporated.For example, a portion of the p-doped layer of the LED stack may beremoved expose the n-doped layer in order to provide an n-contact areaat the top end of the LED stack. This allows for conductor wires to thecontact to extend upwardly from the display and diminishes the need forspace between LEDs for the contact. A p-contact may also be provided atthe top of the stack to form a rear-drivable LED.

The LED wafer may then be subdivided into smaller portions that definechixels, each chixel having a plurality of LEDs that will serve assub-pixels. The chixels can then be placed on a flexible substrate in anarrangement that allows bending between the chixels and provided withdrive means to form a flexible display. This manufacturing processallows for accurate spacing between the LEDs by using masking, etchingor other known techniques that produce uniformly spaced subpixels.Furthermore, the process allows for the accurate arrangement ofsubpixels between chixels and, therefore, uniform subpixel placementthroughout a display as well as minimal subpixel, pixel, and chixelgaps.

Traditionally an LED wafer is diced into individual LEDs that are thenhoused in separated LED assemblies. These separate LED assemblies arethen incorporated into a display as individual subpixels. Due to theindividual housings of the LEDs, however, that method results indisplays with non-uniform subpixel or pixel spacing and large subpixelgaps and pixel gaps. Furthermore, each individual LED must be providedseparately into the display, resulting in a large number ofmanufacturing operations.

Chixels may be formed by halting an LED wafer production process beforethe substrate is diced to form discrete LEDs. In a typical process forproducing blue emitting LEDs, a layer of p-doped gallium nitride isdeposited on a 2″ sapphire wafer. Then, a layer of n-doped galliumnitride is deposited. A photomask is deposited and the gallium nitridelayers are selectively photoetched to create individual LED units andtheir respective electrodes. In the manufacture of discrete LEDs, thewafer would then be diced, and the LEDs would be packaged. In the chixelproduction process, the wafer is diced, but instead of discrete LEDs,the dicing is performed so that the resulting diced pieces hold x×xarrays of LEDs.

Under an exemplary method of the present invention, multiple LEDs sharea single LED substrate by cutting the LED wafer into larger units,chixels, that comprise a plurality of LEDs that define subpixels andtogether form pixels of a display. This allows for uniform spacingbetween the LEDs, and therefore uniform spacing between subpixels andpixels and results in smaller subpixel and pixel gaps. By manufacturingthe LEDs on the same rigid wafer substrate, the pitch of the LEDs can betightly controlled during the LED wafer manufacturing process usingmasking, etching and other techniques thereby providing a uniformsubpixel and pixel pitch. The LEDs may be provided with contacts and adrive means to form workable subpixels of a display.

Furthermore, the exemplary method allows for different chixel sizes andshapes to be selected during the dicing process and is easily adjustableto different subpixel sizes by changing the etching process. Forexample, an LED wafer may be grown having LEDs of a size 320 micronssquare and separated by 320 microns on each side and then separated intosub-units of 96 LEDs, each LED corresponding to a subpixel of a display.For example, the 96 LEDs may correspond to 8 rows of 12 subpixels. Thesubpixels may be grouped into three to define pixels to form a 4×8 pixelarrangement. Or the LED wafer may be divided into chixels having 48 LEDsubpixels to form a 4×4 pixel arrangement. The subpixel size can bechanged by simply using a different etching mask and the chixel size bychanging the dicing cut lines.

A plurality of chixels, having a plurality of light emitters, which willserve as subpixels of a display, may be arranged on a flexible substrateto produce a flexible display. In one exemplary method the chixels areplaced light-emitting end down onto a flexible substrate so as totransmit light through the flexible substrate. The chixels may bearranged at a predetermined spacing to produce a desired chixel gap toprovide a desired bend radius to the flexible substrate. Drive means maybe provided to the chixels to power the light emitters for emittinglight. The drive means may include a controller to control the lightemitted from each light emitter (subpixel) to produce a desired image onthe display. In one exemplary embodiment a controller is provided foreach chixel to produce a chixel-partitioned display. This has theadvantage of decreasing the number and length of wires and distributesthe size of the controller unit out among the chixels, possibly reducingthe bulk of the display electronics by subdividing them into smaller,though more numerous, units.

In one exemplary embodiment a flexible substrate that may be used inconjunction with the chixels includes a diffusion layer, a contrastenhancement layer, and a hardened outer layer. The chixels may beattached to the flexible substrate by an adhesive or other means so thatlight emitted from the chixel is transmitted through the flexiblesubstrate. The flexible substrate may also include one or more filtersto manipulate the light emitted from the LEDs. For example, thesubstrate may include an arrangement of red, green and blue filters thatcorrespond to the location of light emitters of the chixels to providered, green and blue subpixels of the display.

It is possible to produce an RGB display using monocolor LEDs and eitherfilters or color conversion and filters. Both techniques use blue(gallium nitride, GaN) LEDs. In the first embodiment, blue LEDs may befiltered to allow only red or green wavelengths of light to be emitted.In this case, the blue would not be further filtered for blue lightemission unless it was desirable to emit a different color point. In thesecond embodiment, a white color conversion phosphor is deposited overthe blue LEDs. This results in white light emission that can then befiltered into red, green and blue. The filtering of white to RGB is moreefficient than the filtering of blue to red or green. The filters usedin these embodiments could be provided in the form of a flexible filmonto which the appropriate dyes and/or filter materials have beenprinted in the desired pattern. An example of this type of film is thatused on backlit LCD laptop monitors. In an effort to make the chixel gapless noticeable to the viewer, the filter film area corresponding to theedge of a chixel may be printed with the pixel shape rotated 90°, andLEDs from both adjacent chixels will light the rotated pixel.

In one exemplary embodiment, in which blue LEDs are used, red and greenfilters may be provided to make RGB pixels. As discussed above, the LEDsof the chixel may include a photoconversion layer so that the LEDs emitwhite light, in which case red, green, and blue filters may be used.Arrangements other than standard RGB pattern may be used. For example,in one exemplary embodiment, filters are arranged to minimize thesubpixel, pixel, and chixel gap by providing filters that bridge twoadjacent chixels. For example, a red filter may be placed so as to coversubpixels from two different chixels. Furthermore, although discussed asone light emitter to one subpixel, multiple light emitters may be usedfor one subpixel. For example, each colored filter may include threeLEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flexible display in accordance with an exemplaryembodiment of the invention.

FIG. 2 shows an enlarged view of a portion of the display of FIG. 1along cut line 2-2.

FIGS. 3A-3B show a side view of a flexible chixel display in accordancewith an exemplary embodiment of the invention.

FIG. 4 shows a chixel in accordance with an exemplary embodiment of theinvention.

FIG. 5 shows a flexible display which incorporates square-shaped chixelsin accordance with an exemplary embodiment of the invention.

FIG. 6 shows a flexible display which incorporates square-shaped chixelsof FIG. 5.

FIG. 7 shows an elongated chixel in accordance with an exemplaryembodiment of the invention.

FIG. 8 shows a flexible display incorporating the elongated chixels ofFIG. 7.

FIG. 9 shows a chixel-based display in accordance with an exemplaryembodiment of the invention.

FIG. 10 shows an enlarged portion of the chixel-based arrangement ofFIG. 9.

FIG. 11 shows an LED wafer in accordance with an exemplary embodiment ofthe invention.

FIG. 12 shows a side view of the wafer of FIG. 11.

FIG. 13 shows an LED stack of the wafer of FIG. 11.

FIG. 14 shows a side view of an LED of a chixel in accordance with anexemplary embodiment of the invention.

FIG. 15 shows a top view of the LED of FIG. 14.

FIG. 16 shows a white light emitting LED of a chixel in accordance withan exemplary embodiment of the invention.

FIG. 17 shows an alternative embodiment of a chixel LED.

FIG. 18A shows a top view of an LED wafer in accordance with anexemplary embodiment of the invention.

FIG. 18B shows an enlarged portion of the LED wafer of FIG. 18A.

FIG. 19 shows a chixel separated from the LED wafer of FIG. 18A inaccordance with an exemplary embodiment of the invention.

FIG. 20 shows the chixel of FIG. 19 incorporated into a display.

FIG. 21 sows an enlarged portion of the display of FIG. 20.

FIG. 22 shows a display substrate in accordance with an exemplaryembodiment of the invention.

FIG. 23 shows a side view of a chixel-based display.

FIG. 24 shows a flexible chixel-based display in accordance with anexemplary embodiment of the invention.

FIG. 25 shows a flexible chixel-based display having dedicatedcontrollers for each chixel.

FIG. 26 shows a chixel and filter arrangement for a chixel-based displayin accordance with an exemplary embodiment of the invention.

FIG. 27 a chixel-based display incorporating the chixel and filter ofFIG. 26.

FIG. 28 shows an exemplary embodiment of a chixel having additional edgelight emitters.

FIG. 29 shows a color flexible chixel-based display incorporating thechixel of FIG. 28.

FIG. 30 shows an enlarged portion of the display of FIG. 29.

FIG. 31 shows an exemplary embodiment of filter pattern.

FIG. 32 shows an exemplary chixel and filter arrangement.

DETAILED DESCRIPTION

As required, exemplary embodiments of the present invention aredisclosed herein. These embodiments are meant to be examples of variousways of implementing the invention and it will be understood that theinvention may be embodied in alternative forms. The figures are not toscale and some features may be exaggerated or minimized to show detailsof particular elements, while related elements may have been eliminatedto prevent obscuring novel aspects. Therefore, specific structural andfunctional details disclosed herein are not to be interpreted aslimiting, but merely as a basis for the claims and as a representativebasis for teaching one skilled in the art to variously employ thepresent invention.

For purposes of teaching and not limitation, the exemplary embodimentsdisclosed herein are discussed mainly in the context of LED lightemitter technologies. However, the present invention is applicable toother light emitting technologies as well, such as, by way of exampleand not limitation, backlit LCDs, electroluminescence, or plasma tubesor cells.

Turning to the figures where like elements have like reference numbersthroughout the several views, FIG. 1 shows an exemplary embodiment of aflexible display 100. As shown in FIG. 2, the flexible display 100 iscomprised of a plurality of pixel chips 202, referred to herein aschixels 202, that are arranged in a chixel arrangement 200. The chixels202 may be rigid self-contained components that include a plurality ofpixels 204, formed of subpixels 206. The chixels 202 are of asufficiently small size and attached to a flexible display substrate 208in such a manner that the space between the chixels, referred to hereinas a chixel gap 304, allows the flexible display substrate 208 to have abending radius to provide a desired flexibility to the display 100.

For example, as shown in FIG. 3A, chixels 202 are provided on a flexibledisplay substrate 208 with a chixel gap 304 of a size so that the sideedges of the chixels are parallel when the substrate 208 is flat. Asshown in FIG. 3B, as the substrate 208 flexes, the chixels 202 move atangles with respect to one another due to the bending of the substrate208 at the chixel gaps 304. Although shown as square chixels 202 withsharp upper corners, the chixels 202 could have rounded corners or othershapes to prevent contact between adjacent chixels 202 during bending ofthe substrate 208. Furthermore, the chixels 202 could be shaped so as tolimit or prevent flexing of the substrate in a particular direction. Forexample, the chixels could have extensions (not shown) that contact eachother to limit movement when the display is flexed in a particulardirection. The size of the chixels and spacing between the chixels couldalso be varied to provide desired flexibility. For example, smallerchixels could be used on portions of the display which require moreflexibility and larger chixels used on portions with lower flexibilityrequirements.

The chixels 202 are of a predetermined shape and arranged in a desiredpattern on a flexible substrate 208 to form a flexible display 100. Thesize, shape, and arrangement of the chixels 202 may be selected toprovide a desired bend radius to the flexible substrate 208 to which thechixels 202 are incorporated.

As shown in an exemplary embodiment in FIG. 4, a chixel 202 may begenerally square in shape. For example, the chixel may comprise a 4×4array of 16 pixels 204, each pixel having three subpixels 206. As shownin FIG. 5, this square shape allows a chixel-based display 500 in whichthe chixels 206 are incorporated to flex easily both horizontally andvertically between the chixels 202 as the ratio of vertical andhorizontal chixels gaps 304 is the same. FIG. 6 shows a chixel displayhaving chixels 202 on a flexible substrate with sufficient bend radiusto be rolled up into a tube having a radius of approximated by:

${r = {{\frac{n - \pi}{2\pi}x} + {\frac{n\; s}{8\pi \; x}\sqrt{4_{x}^{2} - s^{2}}}}},$

Where x=width of a chixel; s=width of space between chixels; andn=number of chixels in the tube; and provided that n≧4, x≧0.5 s, andassuming the tube cross-section is circular.

Chixels 202 may be provided in other shapes and arranged to provide achixel gap 304 of an appropriate size to provide the display 100 with adesired amount of flexibility. Generally, the smaller the chixel 202,the greater the number of chixel gaps 304 in the display in which thechixels are incorporated and the greater the number of bending pointsthat can be provided and, therefore, the greater the flexibility of thedisplay. For example, if it is desirable to provide a greater amount offlexibility in one direction of the substrate than another then thechixels can be shaped to provide such flexibility by arranging a largernumber of flexible gaps in the one direction than the other.

The chixel 702 shown in FIG. 7 includes a 4×8 pixel arrangement. Asshown in FIG. 8, this allows for greater lateral bending because thereare approximately twice as many vertical bending points 804 in thedisplay than horizontal bending 806 points. Although the smaller thechixel, the greater the number of chixel gaps and the greater theflexibility of the display, the fewer the number of pixels that can beprovided on the chixel and/or the smaller the pixels. Thus, while havingsmaller chixels increases flexibility, having larger chixels increasesthe size and/or number of pixels that can be provided on each chixel anddecreases the number of chixels that must be attached to the flexiblesubstrate. Thus, smaller chixels could be used in areas of the displaywith higher flexibility requirements.

As shown in FIG. 4, a chixel 202 may include pixels 204 that arecomprised of subpixels 206. The subpixels 206 may have differentproperties in order to provide desired properties for the pixel 204 ofwhich they form a part. For example, the pixels 204 may comprise red206A, green 206B, and blue 206C subpixels that together form an RGBpixel. The intensity of the individual subpixels 206A, 206B, 206B can bemanipulated to provide light having desired characteristics, such as adesired light color or brightness. The subpixels 206 may have arectangular shape so that together they form a square-shaped pixel 204.For example, each subpixel may have dimensions of ⅓ mm×1 mm to form apixel of 1 mm². The pixels 204 may be provided in a 4×4 array on a rigidsubstrate 220 to form a chixel of about 4 mm. The substrate 220 may betransparent to allow light emission through the substrate. For example,the substrate may be rigid glass or sapphire as discussed in more detailbelow.

The pixels 204 may be provided at a distance apart from one another, thedistance referred to as a “pixel gap” 304. The size of the pixel gap 304may vary depending upon the particular light emitting technology usedfor the subpixel 206. For example, some light emitters may requireconductors that extend around the edge of the emitter, which preventsthe light emitters from directly abutting each other, thereby resultingin large subpixel and pixel gaps. For example, Organic Light EmittingDiodes (OLEDS) generally require that current be provided through thefront of the display and a contact is commonly arranged to extend aroundthe edge of the OLED, thereby preventing OLEDs from being tightly packedin a display.

One problem with prior art displays is that the pixel gap 304 is of suchsize that gap lines are visible in the resulting display which isdistracting to a viewer and renders an image of poorer quality. This ledto prior art attempts to provide front conductors for the pixels. Thisfront conductor approach raises additional problems in producingflexible displays, however, due to the limited flexibility and highresistance values of known transparent front electrodes.

In one aspect of the present invention, the pixels 204 are sizedrelative to the pixel gap 306 between the pixels 204 such that the pixelgap 306 is less noticeable to an observer. For example, in a prior artOLED device the gaps between pixels that are required for thewrap-around electrodes can result in a pixel gap to pixel area ratiothat is readily noticeable to a viewer of the display.

In the present invention, pixels 204 are sized relative to the pixel gap306 so that the gap line is less noticeable while still providing adesired resolution. For example, in the exemplary embodiment shown inFIG. 4, the pixel gap d2 may be 0.25 mm and the pixel size (width orheight) 1 mm to produce a pixel gap to pixel size ratio of 0.25 mm/1mm=0.25. Applicant has found that for a 120″ display at 1080p a pixelsize of 1 mm² is desirable.

One advantage of the present invention is that if a 4 mm chixel 202which includes 16 pixels in a 4×4 array is used to provide the pixelsfor the display, the number of operations to provide the pixels 204 tothe display is 1/16 of that of a technique that attempts to attachindividual pixels to a display because multiple pixels are added with asingle chixel. As discussed in more detail below, minimizing the effectof the gap line allows for the use of manufacturing techniques andresulting structures that were previously avoided due to concerns overgap lines. For example, by adjusting the pixel size to the pixel gap tominimize the effect of a gap line allows for electrodes to extend aroundthe side of a pixel and allow a display to be driven at the rear,thereby eliminating some of the problems with prior art devices that arefront driven.

As shown in FIG. 9, chixels 202 may be coupled to a flexible displaysubstrate 208 by an adhesive or other coupling means. The pixels 204 canbe arranged on the chixel 202 with uniform pixel spacing of a pitch orpixel gap d2. The chixels 202 can be arranged on the flexible displaysubstrate 208, to maintain the uniform pixel gap 304 d 2 betweenadjacent chixels 202A, 202B. For example, the pixels 202 may be locatednear the edges 910A-B of the chixels 202 and adjacent chixels 202A-Barranged so that the pixel gap 306 is uniform between pixels 204 evenacross adjacent chixels 202A, 202B. As discussed above, the chixel gap304 between the chixels 202 provides a desired bend radius to theflexible substrate 208 that allows the display 100 to flex. Thus, auniform pixel gap and a desired flexibility can be obtained; in otherwords the pixel pitch is consistent in both the rows and columns, evenbetween pixels on the edges of two adjacent chixels. In one exemplaryembodiment the pixel gap may be 320 micron, the chixel gap 320 micronand the pixel size 1600 micron.

As discussed in more detail below, the flexible substrate 208 maycomprise a variety of layers, such as by way of example and notlimitation, a contrast layer, a diffusion layer, a filter layer, and ananti-reflection layer. Each of these layers may be of a flexible plastictype. Thus, even though the chixels 202 themselves may be rigid, asufficient number of chixel gaps 304 are provided in an appropriatearrangement that a desired bend radius of the flexible substrate 208 isobtained.

Chixels 202 may employ different light emitting technologies, such asLED, electroluminescence, plasma tubes or cells, and backlit LCD. FIGS.11 and 12 show an exemplary method of manufacturing an LED-based chixel.An LED is formed by depositing an n-doped semiconductor and a p-dopedsemiconductor layer on a substrate. Light is formed at the p-n junctionwhen it is excited by electrical current. As shown in FIG. 11 an LEDwafer 1100 may be produced that includes a plurality of spaced apart LEDstacks 1104 that, as discussed in more detail below, may serve as lightemitters for a flexible display. As shown in FIG. 12 the LED wafer 1100may comprise a rigid substrate 1102 having a plurality of LED stacks1104 thereon. For example, as shown in FIG. 13 an LED stack 1104 mayinclude a p-doped layer 1106 and an n-doped layer 1108 that are providedatop a sapphire substrate 1102 and have the appropriate properties toemit light when supplied with an appropriate charge (current).

Various techniques can be used to create the LED stacks with greataccuracy. Portions of the layers 1106, 1108 may be removed to createseparate LED stacks on the rigid substrate separated from one another bya gap 1110 that generally corresponds to a subpixel or pixel gap of acompleted display. For example, a mask may be applied and etchingtechniques used to etch channels through the upper layers 1106, 1108down to the substrate to produce stacks that share a common substrate1102. In an exemplary embodiment LED stacks may be generally squarehaving a length of about 320 μm and a width of about 320 μm and a gapbetween the LED stacks 1104 of about 50 μm. Applicant has found that alayer of n-GaN of about 0.2 μm thickness and a p-GaN layer of about a0.2 μm thickness on a sapphire substrate of a thickness of about 350 μmcan be used to produce LEDs that emit blue light having a wavelength ofabout 450 nm. Different layers may be used or additional layers added tothe LED stacks to obtain LEDs that emit light with desiredcharacteristics. Furthermore, as discussed in more detail below,filters, photoconverters, and other apparatus may be used to manipulatethe light emitted from the LEDs.

In order to make the LED stacks 1104 into workable LEDs, a p-contact1120 and an n-contact 1122 may be provided to the stacks 1104 as shownin FIG. 14 to form an LED 1400. The p-contact 1120 may be provided in acutout area 1130 of the p-doped layer 1108. For example, an etchingprocess may be used to remove a portion of the p-doped layer to allowthe n-contact 1122 to be placed directly on top of the n-doped layer1106. This allows the p-contact to be placed directly atop of then-doped layer 1106 and conductors 1140 to extend upward from the LED toa rear mounted display driver when the LEDs are incorporated into adisplay. This obviates the need of providing a large space between thelight emitters for providing a pathway for conductors running along theedge and side of the light emitter and thereby allows the LEDs to betightly packed. The wafer may be processed by etching, ablation, orother known techniques to form LEDs of various shapes, such as the LED1700 shown in FIG. 17 and arranged in a desired arrangement.

Additional layers can also be added to the LEDs 1400. For example, asshown in an exemplary LED 1600 in FIG. 16 a luminescent phosphor layer1610, typically a powder phosphor formulated based on the light outputof the LED to provide the best conversion, may be provided for colorconversion, to convert the emitted blue light to white. The colorconversion layer 1610 may be added by known techniques. As shown inFIGS. 14 and 16 when an appropriate current is applied, light istransmitted downwardly from the LED 1400, 1600. Thus, in theseembodiments the substrate 1102 is transmissive.

The wafer 1100 may include different layers on different LED stacks toprovide different light characteristics. For example, different layerscould be used to produce red, blue, and green light from different LEDstacks 1104. The wafer 1100 could also be made of uniform LED stacks1104 having the same or similar properties. For example, the LED stacks1104 could be constructed to emit white light or blue light which couldthen be filtered to produce light with desired characteristics. In theexemplary embodiment shown in FIG. 14 in which GaN layers are used, bluelight is emitted. Filters may also be used to provide red, green andblue LEDs which could define red, green and blue subpixels of an RGBpixel display. As seen in FIG. 16 a white phosphor photoconversion layer1610 can be applied so that the light emitted from the LED 1600 is whitewhich is more efficiently filtered than blue light.

As shown in FIGS. 18A-B an LED wafer 1800 may include an array ofuniformly spaced rectangular-shaped LEDs 1802. The LEDs 1802 definesubpixels 1803 that may be incorporated into a flexible display. Thesubpixels 1803 are spaced apart a horizontal distance hi that forms asubpixel gap 1808. A group of LEDs, such as three LEDs, may be used todefine an addressable pixel 1804 for a display. A larger array of LEDsmay define a chixel 1806 which may include multiple subpixels andpixels. In the exemplary embodiment shown in FIG. 19 the chixel 1806includes 8 rows of 12 LEDs which define 96 subpixels and 32 three-LEDpixels 1804 of the chixel 1806 to provide a 4×8 pixel arrangement.Commands/instructions from a driver may be directed to the LEDs of thepixel grouping to manipulate the individual LEDs 1802 as subpixels sothat the overall light produced by the pixel 1804 is of desiredcharacteristics, such as a desired color and brightness.

Multiple chixels 1806 may be coupled to a flexible substrate 208 to forma flexible display 2000. For example, as shown in FIG. 20 chixels 1806may be coupled to a flexible substrate 208 in an arrangement 2202. Thearrangement of the subpixels 1803 on the individual chixel 1806 inconjunction with the arrangement of the chixels 1806 on the substrate208 may be such as to provide uniform LED spacing and hence uniformsubpixel and pixel spacing across the display 100. In addition, thepixel gap 306 may be uniform across the display and may be set equal tothe pixel gap 308. By providing the subpixels 1802 about the edge of thechixel 1806, and removing a predetermined amount of the substrate 208 inthe dicing process, the chixel gap 304 may be such that the pixel gap306 between pixels on adjacent chixels 202 is the same as the pixel gapbetween pixels on the same chixel and the pixel gap is equal to thesubpixel gap. This provides for a uniform display with minimal gaplines. While discussed primarily in terms of the lateral spacing of thesubpixels, pixels, and chixels, the same principles apply to the spacingof the subpixels, pixels, and chixels in other directions, such as thevertical gaps.

The size of the pixels 1804 can be varied depending upon the desiredresolution and use of the display. For example, the size of thesubpixels and pixels 1804 within a chixel 1806 incorporated into adisplay intended for use at a viewing distance of 10 feet may be smallerthan a display meant to be used at a viewing distance of 100 feet, eventhough the displays have the same resolution.

As discussed above, the chixels 202 may be coupled to a flexiblesubstrate 208 to form a flexible display 100. In addition to providingsupport to the chixels 202 the substrate 208 may also provide additionalfunctions, such as filtering, light diffusion, contrast enhancement,etc., and may be comprised of multiple layers. An exemplary flexiblesubstrate 2200 shown in FIG. 22 comprises a diffusion layer 2202, acontrast enhancement layer 2204, and an outer protective layer 2206. Theflexible substrate 2200 may also include an adhesive layer 2208 forcoupling chixels 202 to the flexible substrate 2200 and one or morefilters 2210, as well as an anti-reflective layer 2212 (not shown).

The chixels 1600 may be placed light-emitting end down on the substrate208 as shown in FIG. 23 so as to emit light through the flexiblesubstrate 2200. The exposed p 1120 and n 1122 contacts allow the displayto be driven from the rear by a drive system 2402 as shown in FIG. 23,thereby avoiding the complications of providing transparent frontelectrodes to the LED subpixels. As discussed above with reference toFIGS. 3A-3B the chixels 1600 are arranged on the substrate 2200 so thatthe resulting chixel gaps 304 provide sufficient bending areas to givethe substrate 2200 a desired amount of flexibility. The drive means mayaddress the subpixels in predetermined pixel groupings.

As shown in FIG. 22 the substrate may be provided with one or morefilters 2210 to manipulate the light emitted from the LED lightemitters. For example, an array of color filters can be printed, sprayedor otherwise provided to the substrate 2200. As seen in FIG. 26 ared-green-blue filter arrangement 2602 having filter portions 2604A,2604B, 2604C of red R, green G and blue B may be added to the substrateassembly 2200 to form a filtered substrate 2702 with filter portions2604 that correspond with the different LED light emitters 1600A, 1600B,1600C of a chixel 1600. The chixel 1600 is coupled to the filteredsubstrate to form a color display 2700 so that the light emitters 1600align with the filtered portions 2604 to form RGB pixels 2702A, 2702B,2702C as shown in FIG. 27.

As shown in FIG. 24 drive means 2402 may be provided to the chixels toprovide the necessary power and commands to make the light emitters ofthe chixels emit light in a desired manner. The drive means 2402 mayinclude drive electronics as known in the art. In the exemplaryembodiment shown in FIG. 25, a controller 2502 is provided for eachchixel. The controller 2502 may comprise a data line and a power linethat controls the emission of light from each of the light emitters on aparticular chixel 1600. By providing individual chixels with acontroller 2502, chixel units can be provided which can be premade andready to install in a display.

Other filter arrangements may be provided in lieu of the standard RGBfilter arrangement discussed above, in which each filter covers a singlelight emitter. For example, in the exemplary embodiment shown in FIGS.28-30 edge filters 2804 are arranged horizontally to cover portions ofmore than one light emitter. These edge filters further minimize theeffect of the chixel gaps 304. In addition, the chixels may be sized toinclude edge light emitters in addition to standard three-subpixelmultiples.

Chixel gaps may to be more noticeable when the display 100 is flexedinto a non-flat condition. As shown in FIG. 28 in addition to thestandard lateral RGB filter arrangement of the filter arrangement 2602in FIG. 26, the filters that correspond to light emitters 1600 at theouter edge of a chixel 2802 referred to as edge emitters 2810 may besized and shaped to cover edge emitters of two adjacent chixels 2802.For example, edge filters 2804 may be provided to bridge the chixel gap304 between adjacent chixels 2802 and cover edge light emitters 2810 oneach chixel 2802. These edge filters 2804 may be oriented horizontallyand may be of a size as to together cover an edge light emitter 2810 onadjacent chixels 2802 in a vertical RGB arrangement. For example, asshown in FIG. 28 a row of 14 light emitters 1600 on a chixel 2802include 12 center light emitters and two edge emitters 2810. The chixel2802 may be arranged on a filtered substrate 2906 having vertical filterportions 2604 and edge filters 2804 so that the center 12 light emitters1600 correspond with a row of 12 vertically oriented red 2604A, green2604B or blue 2604C filters and the two edge light emitters 2810correspond with colored edge filters 2804A-C.

Instead of covering a single light emitter on one chixel, the edgefilter are sized and oriented to cover an edge light emitter 2810 oneach chixel thereby bridging the chixel gap. In addition, the edgefilters may be of a size such that multiple edge filters cover theadjacent light emitters. For example, red, green and blue edge filtersmay be arranged to cover adjacent edge light emitters in a vertical RGBpattern. The same may be done along the upper and lower edges ofadjacent chixels. In addition to having the 12 RGB filters whichcorrespond to 4 RGB pixels, an extra light emitter may be provided ateach edge of the chixel to form a row of 14 light emitters. Thus, whentwo chixels are placed next to one another two edge pixels/lightemitters are adjacent one another. It should be noted that while thesubpixels and filters are generally discussed as corresponding with asingle light emitter, filters may cover multiple light emitters. Forexample, a subpixel of a chixel could include three vertically alignedlight emitters which could be cover by a red filter to define a redsubpixel.

FIG. 31 shows another exemplary filter pattern 3102 that may be used inconjunction with a chixel 2802 in which upper and lower end filters 3104are elongated to filter adjacent upper and lower light emitters 2820across the chixel gap 304 in FIG. 32. Although each upper edge filter3104 is shown as a single color filter that covers two adjacent lightemitters from adjacent chixels 2802A-B, the filters could be sized sothat each light emitter is covered by a red, green, and blue filter.

1. A flexible display comprising: a plurality of pixel-containing chipsattached to a flexible substrate with a bend gap provided betweenadjacent chips so as to allow the flexible display to bend in a firstdirection along a bend radius.
 2. The flexible display of claim 1,wherein each of the plurality of pixel-containing chips comprises anarray of pixels.
 3. The flexible display of claim 2, wherein each pixelin the array of pixels comprises a plurality of sub-pixels.
 4. Theflexible display of claim 3, wherein each of the plurality of sub-pixelscomprises a light-emitting diode.
 5. The flexible display of claim 1,wherein each of the plurality of pixel-containing chips comprises aplurality of light emitters affixed to a rigid substrate.
 6. Theflexible display of claim 2, wherein a first pixel gap is providedbetween adjacent pixels on each of the plurality of pixel-containingchips and a second pixel gap is provided between adjacent pixels onadjacent pixel-containing chips; and wherein each of the plurality ofpixel-containing chips are positioned and arranged such that the firstpixel gap and the second pixel gap are substantially the same anduniform across the flexible display.
 7. The flexible display of claim 1,wherein the flexible substrate comprises a filter film.
 8. The flexibledisplay of claim 1, wherein each of the plurality of pixel-containingchips comprises rear contacts adapted to receive current from aconductor, the rear contacts provided on a side of the chip opposite theflexible substrate.
 9. The flexible display of claim 1, furthercomprising a display driver electronically connected to the plurality ofpixel-containing chips and adapted to generate a display on the flexibledisplay.
 10. The flexible display of claim 1, wherein the flexiblesubstrate comprises a contrast enhancement layer.
 11. The flexibledisplay of claim 1, wherein the flexible substrate comprises a diffusionlayer.
 12. The flexible display of claim 1, wherein eachpixel-containing chip is adapted to transmit light through the flexiblesubstrate.
 13. The flexible display of claim 1, wherein the flexibledisplay is sufficiently flexible to roll into a cylindrical shape. 14.The flexible display of claim 1, wherein the flexible display is adaptedto bend in a horizontal direction and a vertical direction.
 15. Theflexible display of claim 1, wherein the flexible display has a pixelgap to pixel size ratio equal to or less than 0.25.
 16. The flexibledisplay of claim 2, wherein at least one pixel in the array of pixelscomprises: a rigid substrate; a first layer of n-doped gallium nitrideon a rigid substrate, the first layer of n-doped gallium nitridecomprising a first surface portion and a second surface portion; a firstlayer of p-doped gallium nitride on said first surface portion; a firstelectrical contact contacting the first layer of p-doped galliumnitride; and a second electrical contact contacting the second surfaceportion of the first layer of n-doped gallium nitride.
 17. The flexibledisplay of claim 16, further comprising a second layer of n-dopedgallium nitride on the rigid substrate, the second layer of n-dopedgallium nitride comprising a third surface portion and a fourth surfaceportion; a second layer of p-doped gallium nitride on the third surfaceportion; a third electrical contact contacting the second layer ofp-doped gallium nitride; and a fourth electrical contact contacting thefourth surface portion of the second layer of n-doped gallium nitride.18. The flexible display of claim 16, further comprising an electronicdrive unit electrically connected to the first and second electricalcontacts.
 19. The flexible display of claim 17, further comprising anelectronic drive unit electrically connected to the first, second,third, and fourth electrical contacts.